SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6bea446a0a6e711fe233934d263a8104aa0cbe15e2dac1d5196a69b2f2fa1af' 
  AND token = 'Jcy6t6RMo5W8ZqDOAdz8Ij1ivrCrw0+zLawJtZqMl6Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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