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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b39b13da5d0b2187050825065f1febc5fa0c9a3753be22fdf2021291bcb280c7' 
  AND token = 'cbFMAZ0a+sOxN//DqsNrWg+guYfzRotps0qSnbQQD70=' 
  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"
    }
  }
}