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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fcf24202931ca65496357fb376f1634d11d98e5211be5560d3470d0231284b69' 
  AND token = '+kLEb03yeVoisrw5JvhiUcfKqBse+ATT7exr1SpSeVc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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