SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81ac4132ab6814ad39697fcbb217c46a545a1759765faa1701ee8354c6df6ad2' 
  AND token = '8WhNGiBfDRBGEHY7io305B3kHD/3KhD7gQ70HIBO62s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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