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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3cb41d2a5c4f2a371937f10ad8f0dbda9c3e75e936a87fff10cdd50d1c1b10a5' 
  AND token = 'MCqwbCo7DCkOz0fxlLmM/dPh6UKlG+iTM861FhOr3sQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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