SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dfeff02b33efe7112d5025e8cb4f281ac532fe2429fa70478f218c78c3b5724' 
  AND token = 'A7fv4VBywiWbPIfYHbb61N7rCgRXSsHDnPLkOfGJtXE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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