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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ebb49c1e1c553046012f7dc4209084fe0c0e8da696d065523f2e59c19c59138' 
  AND token = '9cHHYkj83HWS6ySExo09GM8zz880mS578r8HG7vCFLM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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