SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be66f926b6fa7d5273ee1fcb28ec8e98500146d0443053384f409b02cfd91ee4' 
  AND token = '+doszKOtxj9JzvdypqnS2mJWaHgsDsZXpFFUeLEX8WY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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