SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b56f14bce900ea6b198d683b8f10747859183cafdc6a2c08237efbd7ba9e300d' 
  AND token = 'jmrv9CoZswTzLVgI8qH6lhHGmhZAfL0s+fmWFLhZpz0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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