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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '902804e8f6e7060a26649f35d9b757c4450da58f233a97413fc66ebfb9659dcf' 
  AND token = '3/uppui7TKh+f7cMfdfDqh2MQrLmI5CYANDkAGCzETU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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