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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8639ee1f42dfb992dfdc59b004c34a6faf7ce18d93b6ff794015561de4339c9' 
  AND token = 'G7n8FHtjZEdFPSyjFuzsz6HGpp5Mv/Da/e5ihQ5DTAI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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