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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d4ee460f676c112e61c3db1371844f9339c8cd76ae656b8f25370a91aed203d' 
  AND token = '3NdO4XQbyl2lodc47kGIZsruQiqL2tskpWLYvZPAcLc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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