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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51da8a74fa7aca7c76ead65fb6cd3dc7d0d9ebbdbfadf57f97bd132d7b574642' 
  AND token = 'uaPz+oq6GiPoxP0EL+wwOUblVq/1xqe36IBBIsBn2Gw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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