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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b59c8ff1d72be19905bbcb9f26a499f42de508cef9872edcf48f7302723b33e4' 
  AND token = 'dkl7UAUTQDIRe+trhoUQHvAAO3guUYZVSlGG+38NjDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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