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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8398f383d8bab29357d499c0dfeb8c92b24e4dd357a1e05e1fafec3f1aa0cd8f' 
  AND token = '+wakLYSnuQBwLNuhiWZSD5TZ9AoZpVWoLdNnw6GTGRE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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