SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '738a7c086a07c007980e4ab96ce699351698fc2073358385d4879667b7b2ef40' 
  AND token = 'MRKxNPMQL7MKsu5tiL68szmfQ1NWTMb3KLBodr+71fY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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