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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3f5250cbfd1b99ad8945ababda26ee3d073ed49603b6793d5acb547e0bd8f68' 
  AND token = 'uNkN0KRqx1goxOznccNabQ5VWEPvBjXEM2CMZ0sUVUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}