SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6535b7d412eca37ef7ba4c3cbd94bccc04de96d1d9ea68731ed26ef1e72d43a' 
  AND token = 'xNqyvF5mldbtpaoJ4jgWrExhVXc2foyoqBg9DhVx75A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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