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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6080f6269888b1d8b38cc50ee4ea4ba56f9cf43a49cf7e6e9983657a4bb54b0' 
  AND token = 'vI+4ezMmMgZ0hmtpfR9ZuD4g/aEgKyKSB0UR7OC0dg8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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