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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be4c3b6cf17566ec2bc5ea5e2fbe05673fc207d5c8f9f4d6f0d110ad8268822d' 
  AND token = 'xNK50ix5a0t7pJ/tpYp4+ObNRSSTp6EZBwyCihFgMWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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