SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b548e3b1f6f8d4004602f64812ba2ed2d51058d808732d50c7ec535ee076354b' 
  AND token = 'tvFK+j8zw6LxgiYsDsCZZRIdhY3hTLHUq8AVeNBuVPc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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