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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb3e2acca0afcbb968cff0492ea39fdd8911ba53b7855c8d1b07f6e486652dc8' 
  AND token = 'PoL5G2LIJrK1SkIapTngxXDyFKQmUJIsRd/lF1UrDPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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