SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6559fffc0e2c27ef2924664893c925947b40788ce30f2cb0b51d6513d3f6af9' 
  AND token = '1WEL1N+zWg8J4YAYwPMlvzfF6ObQO2kANTw6+oHBiI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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