SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af6a4ef89b4d0ee822d0a355be6a13a056857cc53e3980a50c66e0a7755aa6f8' 
  AND token = 'avA3i2ZHD5wNctTXSii0v2vbwikknvs/6u2EEAaLBqs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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