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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0c35e2f64eb8f407f18e06e4cb4f91d965a18880978a2d8e94e9c31e4fc15ddd' 
  AND token = 'KfjMYiwZ6MBWCyUgybIWPOB4Q6hmAIhICtCHjGk0iSQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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