SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54f21dc57b296f96dba757e24167d7050adfde6d84f631cc35c9814501a71720' 
  AND token = 'SVciB+rg97fSoz9NA8QGJf/coUg9FQupg6tDh17cdZk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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