SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '44460808b13a66288c755332a66c0c487ec6c2a1f16e2ebe6644c2142f5cfc06' 
  AND token = 'R/ClNgpQL4qLV7Kh5XtiyjzQwsXTtL3V+/lQ1BfPZPA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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