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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1849fc25f8db3009ba0b4cf4e892584e6eed6b294c9b87bf1d40ab968637f918' 
  AND token = '81wjwSR1i83Us27UKpHw94nQYny7nIFCc1VXkvn8RWk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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