SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3876aa0d925360ab015608c139ac1590b34536205e9e5a47df82f97421344b6' 
  AND token = 'MTJJ7s2lgm3lvr3/ShhDDsPYdZUVeNkKmyJzRf4obig=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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