SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '873726cac081f08c490c3e1ff80c593966eaef4930576651d3e4d9062aa76743' 
  AND token = '8TUzTZsIaYhq7wHIdpzKMiAUVgWbSc6KfN20LufcPDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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