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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8402b39ad7e97d5378e9fde5ceb423f3390769a5fdd332a41ded0e76a8203be' 
  AND token = 'eI6UTZ4YUOQzB3mzwyHg1hK7jTOcGCSEjmzK7idyGhg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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