SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af4fcc0ed0c4fca9e3b2813da26bf978fefb15223c741068dc298899d5fda076' 
  AND token = 'xLBelutJQjMOrLpYu5YGSBwIdkHMJNVZB/5evALqmtk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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