SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7983c3fd277bbcd771cefe9d4b0fa1e19b488367c8b7b07c4f2ba7883a898dd' 
  AND token = 'UvO6ffgVDCjqx8kNuxOYdkqVIcpbnvstESmVdAaF0C0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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