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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b4588ff382a83fbd52b2ff0602f08698367b0c163f68b2f406aad73d457df8f9' 
  AND token = 'qdT9PVFlsIwAsEnuZ3LrHCtozSF45cT9rfVnjoPLE4Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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