SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '99508cc209091d9e54f6b279557a685067d858b3afb414bff8a33d90139df096' 
  AND token = 'i8QmQI1+oXRe7wDubo/l2CzNyXWKHpPUh2Cy+T/CUBA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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