SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '19c9bf5871e108007d0128810a420fbf0a268b870d0850dedded9a3fcfe7364c' 
  AND token = 'eSca3q1qNmZoz7XDbJxhYK+TigAqJxpH199IaL9nuzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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