SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21364315521c4c7a97da75047f936f6635af29d0bd22df5c855b2fc29e9215b' 
  AND token = 'jMJIopgV2qIO+FdSc3YWYGesEdmdIBD1IvqgU3UZfSY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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