SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '510de8aab88ca1a23220fec8c88b3a5bd7e6b94d8695245f97112089950a7f54' 
  AND token = '20wA+abQmw7yPaMEMwhnFoxBUxE9yALCbZOtdGXtxek=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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