SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b291297c99f9b04608a2cdb76a9c80efe4b63348bf91f3166dc3bea7641fc2a9' 
  AND token = 'tRBioO4D1LKVrCpDVw2NGH4mwuUaBMfsg+s5V/lAh3Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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