SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a0ea510418bcf92f963923efd703b9f8ec21942d08eccf003c2ebd0e1c81459' 
  AND token = 'YMNkElg5VzXTH3ZxJnglOzJnXnintRrqrxPJ+L8vm6Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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