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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f3849de0c7008f7fe2c55a57462bdc3ae4f1c036ef547fb0c09cc09872ff75b' 
  AND token = 'FxG+JGVMPoDgLdxMYUSJEqoZ0kFZ3qAdujTTX/OMZdk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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