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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad8e6e86ad4c7ba65b352a1a0cc3f50360514510282ae0b5c66daf7659c1c8d0' 
  AND token = 'Kzl5en4yd5bLpxaednIGEBm9h3cRHwuGdlJBK+Ggb/4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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