SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6cc3d09cb35476d5ded136ba2c92e81b6ef84fcba22a026ee0542b7f4df8e81' 
  AND token = 'd4D74ARLT9RfIGTKYYky9vvsJEraCCbLMhzdrc2gim8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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