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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4138960460f94f68498e12a64103344ecc4fd52a9332884f1fe31ac7a1db78b' 
  AND token = 'hzODlirwadUyx+ks2zawmezz7RSNMMiFuNbyi4EkjJs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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