SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c255e8aa4cf53a1ad0a7569dc950460c09e96a5b3a6e0d20895e316c9845b7e9' 
  AND token = 'u70+MEjZPDoNbILojazotkYDWAn8U9WmoRBsa8jl9Pc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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