SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8b3ac4df4621fa161bf95c551a6e5f3e53dcdd8afd0b51fd26d276aebaffc47' 
  AND token = 'sWVRPl5FiO6Ht5jlBrAC0oc3GG2+AhqvWQUpl1lWzx8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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