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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e31550514d7170436ed62879e0c1d9eee860222a5697b5c5dcb50ab2d23bc2' 
  AND token = '4W5CQTMNRWc43Zw9HVQKxpDuZGqPCs/AvtQ14DdeAm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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