SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c2713d77d30e342f2eafbc793a61b99470fe2c2b4f82c20bd8a0c1ad7645699c' 
  AND token = '1b+EwMKrH1vRSV6dNiZ3CmVUaIPLC9FcNVJQglZzBqs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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