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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6789cb82ee8e9b8e21c2320322dd3e9744b5c85e296c76b6212e8eac0fc627f0' 
  AND token = 'gDKbUeRFPVqsQcT3xWIKTGrqnXnFtQVaem+i6KfKdBQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}