SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3b279bbbbd6ca255f94e7341f2c2ccd440bf9b8ce617c3b9926ca6dd55a79a9' 
  AND token = 'cThnPm/zUZBbyMjfF+NyvgRWOghQXsdWIbm13WQRfyo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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