SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15ced1767e10e649a9cf05f4ef3db20ed1badc4cd9e3a5601e318f5f3fcf9a21' 
  AND token = 'zu+R1QaWYHuSUPnjncm8lL/BYGLwJN3f9bKlrg9i+C4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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