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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '278351cefb9cf798686e0ea244834bd0deab1c0887288265166493374493c201' 
  AND token = 'NkCqlii1wlyapwmMCgJ4vB55t6dvUu+LKe7J6jIOa20=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}